Brakes pulsating

[epricedright]

My front brakes are pulsating pretty bad once they get hot. I put on new Raybestos Quiet Stop Ceramic pads and new Raybestos quiet stop rotors less than 10k miles ago. When the brakes are cold, there is hardly no pulsating at all, if any. I was thinking my rotors were warped, and having them turned, but being when they are cold, there is no pulsating, I'm wondering if having them turned will do any good. Could it be they only warp when hot and once they cool, the warp goes away? What do you guys think?

[mikeal1892]

i have both the same pads and breaks on the seville no troulbes yet. but i did have alot of issues with the older rotors warping. i would think you would mainly notice it when they are hott. I did have a 94 your same color. and a whote 96 that same body. what can i say i love that body style.

michael s

[BodybyFisher]

Read this article, rotors don't actually warp. When the rotor overheats, brake material transfers from the pads to the rotor and 'grabby' spots are created.

http://www.stoptech.com/tech_info/wp_warped_brakedisk.shtml

There are reasons why front brakes overheat:

1) hard use like racing

1A) hard fast stops (opposite of jack rabbit starts)

2) riding the brake

2) rear brakes that are not picking up their share

4) old rotors that are thin causing them to get hotter

5) calipers that don't fully release

Holding the brakes HARD at stop lights is not good, try to be light on your brakes.

Make sure that when you do brakes that you replace ALL of the brake hardware that you can replace like rubber bushings, etc that the sliders ride on. Read that article.

[epricedright]

Read this article, rotors don't actually warp. When the rotor overheats, brake material transfers from the pads to the rotor and 'grabby' spots are created.

http://www.stoptech.com/tech_info/wp_warped_brakedisk.shtml

There are reasons why front brakes overheat:

1) hard use like racing

1A) hard fast stops (opposite of jack rabbit starts)

2) riding the brake

2) rear brakes that are not picking up their share

4) old rotors that are thin causing them to get hotter

5) calipers that don't fully release

Holding the brakes HARD at stop lights is not good, try to be light on your brakes.

Make sure that when you do brakes that you replace ALL of the brake hardware that you can replace like rubber bushings, etc that the sliders ride on. Read that article.

Thanks Mike! I read that article...2nd time actually. I replaced all the rubber bushings (hardware) while doing my brakes and made sure my sliders were free. I bedded my brakes in after replacement as stated in that article. My question is even if there has been some uneven brake deposits left on my rotors from leaving my brakes on after a hard stop (or from some other way), then I wonder why there is there no shutter and pulsating when the brakes are cold? Only after a few stops and the brakes get warmed up do I get the shudder. I would think if uneven pad deposits on the disk were the problem, I would get the shudder all the time, hot or cold. There is no referance to brakes shuddering only when hot that I saw.

I have replaced many a brakes on many a cars, and this is the first time I've encountered this. The only thing I did diffferently with the caddy is I used the ceramic pads and I bedded the brakes in. So I'm starting to think either the pads/rotors are the problem, the bedding somehow caused the problem, or the Caddy given it's weight is part of the problem...i dunno. What is recommended after coming to a hard stop at a light, instead of leaving your foot on the brake, are we to put the car in park? I've never had a problem before leaving my foot on the brake after a hard stop with any other vehicle.

I've loved these Quiet Stop Ceramics so far because they are so much cleaner than semi's, quiet and stop good....but if they are the cause of my shuddering, I will have to say not again. I will call Raybestos tomorrow and see what bedding procedures they recommend for the ceramics. I wonder if CarX and Midas always beds their brakes in after they're done doing a brake job?

[epricedright]

i have both the same pads and breaks on the seville no troulbes yet. but i did have alot of issues with the older rotors warping. i would think you would mainly notice it when they are hott. I did have a 94 your same color. and a whote 96 that same body. what can i say i love that body style.

michael s

Thanks Michael! How many miles do you have on your brakes? Same year, model and color huh, how funny!. I do Love my Caddy...when she's behaving...

BTW, I graduated from I.U back in '85. Boy do I miss Bloomington! What a fun and beautiful town that is! We went down there last fall...1st time back in more than 15 years, man how the town had changed...just as nice though!

[BodybyFisher]

I am not sure why you are having a problem cold, mine will pulse cold and hot. When I say don't hold the brakes hard, I mean don't hold the brakes hard when they are overheated that is guaranteed to transfer brake material.

[Ed Fenwick]

Aloha,

Are you sure that it is the front brakes? Maybe it's the rear this time. 10K miles is to soon for the roters to go bad unless you aren't tightening the lug nuts the same.

[epricedright]

Aloha,

Are you sure that it is the front brakes? Maybe it's the rear this time. 10K miles is to soon for the roters to go bad unless you aren't tightening the lug nuts the same.

Aloha Ed, I replaced my rear pads and rotors as well at the same time. At first I thought it was my rears too as I couldn't feel a shudder in the steering wheel. But I've applied my parking brake while driving and I can feel the rear brakes grab, with no shudder at all. I've noticed the brakes shudder progressively worse the hotter they get. This has me puzzled. I'll take it to Costco tomorrow and have them rotate my wheels and ask them to pay special attention to the right torque and sequence, time to get that done anyhow. I'm a hate to replace everything as those brakes weren't cheap. I guess I could try a clean up cut on the rotors if the trip to Costco doesn't help. And I guess I could live with it, but...

[BodybyFisher]

See this link, it related to hot shudder and holding the brakes when HOT

http://www.clublexus.com/forums/printthread.php?t=85937

[epricedright]

See this link, it related to hot shudder and holding the brakes when HOT

http://www.clublexus.com/forums/printthread.php?t=85937

Thanks Mike! Nice to read I'm not the only one experiencing the shutter only when the brakes are hot. DaveGS4 had the same problem. Bitkahuna stated turning his rotors helped his shutter. If costco doesn't work, then I'll try the turning I guess. Still don't see how it can help much as they seem true (no shudder) when cold??? If that doesn't help, I'll bite the bullet and replace my rotors.

[Vince P]

Body by Fisher,

Mike,

Thank you for your techncal information.

I would love to have a copy of all the technical sites that you use.

As usually, you are impressive.

Regards to the Big Apple.

Vince P

[BodybyFisher]

Thanks, Vince, I am a computer pack rat, if my computer ever crashes my life will come to a screeching halt.... Let me know what you need or what you are looking for, I will try to help you. Thanks again, Mike

[MAC]

I was told there are/were problems with Raybestos Quiet Stop Ceramic pads being too hard and causing breaking problems—interestingly, the complaint was the hard ceramic pads were warping rotors. I don’t know if this is a rumor started by a competitor or is a valid problem. But maybe you should try a different brand the next time and see what happens.

[BodybyFisher]

This is the reason why I use OEM brake components, they were validated for the car, and if problems crop up they are re-designed. I do however understand chasing better performance, but as the guru used to say, you are now doing the validation, when problems like this crop up, NOW?, you are not sure WTF the problem is, using OEM, eliminates having to validate components yourself and takes away unknowns. I am not being critical here of your choices at all, just stating an aspect of this we have discussed before. I myself have my eye on chamfered drilled rotors... in spite of the fact that I will get shorter pad life.

[epricedright]

This is the reason why I use OEM brake components, they were validated for the car, and if problems crop up they are re-designed. I do however understand chasing better performance, but as the guru used to say, you are now doing the validation, when problems like this crop up, NOW?, you are not sure WTF the problem is, using OEM, eliminates having to validate components yourself and takes away unknowns. I am not being critical here of your choices at all, just stating an aspect of this we have discussed before. I myself have my eye on chamfered drilled rotors... in spite of the fact that I will get shorter pad life.

Not trying to argue with you Mike, but here's an article I read from raceshopper.com

http://www.raceshopper.com/tech.shtml#bedding

that somewhat echoes my feelings about OEM and is an interesting read. Don't get me wrong, I agree OEM is the way to go with most parts, but with some there are better, and I figured brake pads were one of them:

Should I use the same components as specified as OEM?

OEM means Original Equipment Manufacturer.

Translation: A component manufactured by a third-party company and selected for use in the original vehicle. An OEM manufacturer will typically manufacture their part based on specifications and designs supplied to them by the vehicle manufacturer.

Your vehicle manufacturer selects components used in your vehicle based on a variety of factors. These include PRICE, quality, deliverability, and many others.

In most cases, the manufacturer will not select the BEST product available.

If all of the items that went into your vehicle were the best - your car

would cost 5-10 times as much as you paid for it!

The manufacturers certainly make decisions, in most cases, to use an adequate product- that meets their demands for price and quality. They may not use the cheapest component- because it would result in too many warranty returns.

However, there are thousands of recalls every year for components which the manufacturer has deemed defective.

You can check them out for your vehicle here:http://www.alldata.com/recalls/

The vehicle manufacturers make mistakes too!

In the aftermarket, you can choose from a range of lesser-cost, lower-quality components OR higher price, higher-quality components.

You have the choice!

Just because it was specifed as OEM- it doesn't make it better!

All of the components we sell are EQUAL TO or BETTER THAN the OEM specification for the original component.

Remember, Firestone tires were OEM on Ford Explorer trucks .

Did that make them better? Think about it!

I figured ceramic pads were better, since they were known to be quieter, stopped good, and most of all were much cleaner (dustless...and they ARE!). But after doing some research, here's what I'm reading about ceramic pads (not sure if all this is true):

Why don't you recommend Ceramic Brake Pads?

Let's start by saying that ceramic brake pads have a place in the automotive industry. They were designed to be a low-dust, noise-free brake pad. They came into popularity after the discontinued use of asbestos-based brake pads. At that time, semi-metallic pads exhibited problems with higher noise and dust levels.

That being said, I can tell you that Ceramic Brake Pads were NEVER designed to be a performance brake pad! Some companies have done a terrific job marketing their higher-priced, ceramic pads to the consumer as a performance pad. Ceramic brake pads typically have lower friction coefficients, and act as an insulator - raising rotor temperatures in cast-iron disc systems. When you have a vehicle that has persistent braking problems- the last thing you want to do is install components that have a LOWER friction coefficient and that RAISE effective operating temperatures! See our section on how this can cause ' Warped Rotors "

Premium-grade semi-metallic or hybrid pads are more effective for handling elevated temperatures and dissipating heat away from rotors. Most, if not all, semi-metallic pads have a degree of ceramic content ALREADY IN the brake pad.

Premium-grade, semi-metallic pads can offer LOW-DUST, NOISE-FREE Performance without sacrificing stopping power and increasing rotor temperatures!

Most organizations with fleet vehicles and other extreme-service applications already know what we're telling you: High-quality semi-metallic pads offer the best combination of stopping-power and extended-wear of any brake pad type on the marketplace today!

Warped Rotors:

What causes 'Warped Rotors'?

Typically warped rotors are caused not by a failure of the rotor itself.

Warped rotors (in most instances) are caused by the brake pads being operated at temperatures outside of their specified range. When the pads get too hot the pad material actually melts and 'fuses' itself to the rotor surface and creates a 'bump' on the surface of the rotor. In most cases this is not noticeable to the naked eye. This creates an annoying vibration when the brakes are applied. The only solution to this is turning (grinding) the rotors or installing new rotors.

We do not recommend turning rotors: It removes additional metal and reduces the the thermal capacity of the discs.

The best way to combat this condition is to use GOOD QUALITY street performance brake pads which have a higher operating temperature range.

Properly 'bedding-in' the pads and discs is a must.

Tip: Our Temperature Indicating Paint Kit may be useful in determining the

correct brake pad compound(s) for your application:

http://www.raceshopper.com/temperature_paint.shtml

When mounting new rotors- they should be installed on the vehicle and indexed with a dial indicator to minimize runout. New rotor runout is typically between .002" - .005" However, failure to mount the rotors ON THE VEHICLE and measure TOTAL runout can cause a vibration even with brand new rotors. You should check hub runout as well- since a very small amount of hub runout (even as small as .002") can create additional runout of as much as .006" - even with perfectly true rotors.

This is similiar to mounting and balancing tires. Often times a rim and tire combination that would require additional weight to correct balance can be rotated and then require less or no weight to balance.

This means you should test the rotor in a number of configurations and install it in the confirguration which results in the LEAST amount of total runout.

What does the above paragraph mean regarding runout?

And none of the above explains why they shudder only when hot??? But I am now wondering if ceramics were the way to go. It appears possibly not. Unfortunately I purchared some of the same pads for my parents 2003 Explorer. They haven't been installed yet, but it's been more than 30 days and Rockauto said they couldn't take them back. I also ordered the same for my minivn last night, but called them this morning and cancelled those. Not sure yet what type and brand of pads I'm gonna use. Has anyone tried the SP cross drilled and slotted (SP inverted radius chamfer) rotors? They are $165.00 for the fronts. I noticed a few guys on some other car forums had them and loved them...no "warping" issues.

http://www.bestbrakes.com/sp_rotors.shtml

[epricedright]

I was told there are/were problems with Raybestos Quiet Stop Ceramic pads being too hard and causing breaking problems—interestingly, the complaint was the hard ceramic pads were warping rotors. I don’t know if this is a rumor started by a competitor or is a valid problem. But maybe you should try a different brand the next time and see what happens.

Thanks Mac! Your post here prompted me into looking into the ceramic pads deeper. I couldn't find any articles complaining about the Raybestos Quiet Stops Ceramic pads specifically, but I did see a couple articles about ceramics in general...see above. I did see one guy's post on another forum who had the same shudder problem. I was gonna call Raybestos, but they want you to pay $1.75 a minute...what a joke. No email address either! I think I'm done w/ Raybestos for that reason alone. Here's the contact info from their website:

Contact Us

We can be reached at:

Brake Parts, Inc.

4400 Prime Parkway

McHenry, IL 60050

Tech Talk

If you would like to speak to a technical service representative live, please call 1-900-733-8355 for $1.75 per minute between the hours of 8 AM and 5 PM Central Standard Time.

[BodybyFisher]

Only time will tell. This issue is passionate and is a constant discussion, if you go back you will see that Scotty and BBF have gotten into discussions about this issue. What do you think aftermarket guys are going to say, OEM is better?

We are talking validation here, not supplying parts, might they be better in some cases? Maybe in certain applications. Maybe in a 240SX that weights a fraction of my caddy. Maybe ceramic causes more heat? Who knows. Like I said this is a passionate topic more than OIL.

Here are some of the issues:

1) there is a general feeling that somehow OEM braking systems are inferior because you get pulsating without understanding how the system works

2) some people never change and neglect their rear brakes. Hmmm let me think about that, well kudos that your rear brakes lasted so long, but the result of IGNORING the rear, is that, 1) the rear brake system does not get BLED and air is in the system, 2) as a result there is insufficient clamping by the caliper due to air and the rotor overheats and looks glazed blue and black, and, 3) the fluid is not changed to get out moisture, dirt, etc, so it more easily boils.. So, the rear does NOT pick up its FULL FAIR SHARE and THAT puts more BURDEN on the FRONT to STOP the car (which as we know does most of the work anyway, but NOW it does ALL the work)... What does that cause, THAT causes the front rotors to OVER HEAT! The overheating facilitates the transfer of brake material to the ROTOR and you have pulsation... It happens OVER and OVER and you think the OEM system SUCKS, and you buy aftermarket pads and drilled rotors but never touch the rear. All of a sudden you think that the drilled rotors work and they do, but they do for a hidden reason, the reason is because they can shed more heat and as a result they don't "warp" meaning the material is NOT transferred as they don't get as hot. See proof of how hot they run here, click each rotor type > http://www.powerstoprotors.com/ But the real problem still exists and its that you have AIR in your system and the rear is INCAPABLE of picking up its share and the pads are glazed. When you look at the rear rotors they are obviously overheated and black.

3) there is a misconception that the rotors somehow actually WARP, but they don't... Can there be run out, yes there can be run out, but the pulsing is generally caused by material transfer, this problem is especially serious in racing. Run out from debris on the flange or wheel, lug studs being bent can happen. Thickness variation from not turning the rotors doesn't help as it gets worse with new pads.

Improper brake repairs to me lead to problems and the thought that OEM is somehow inferior. Not replacing bushings, slider kits, worn parts, not turning rotors, not bedding, not cleaning and lubing the sliders all contribute to a lousy brake job. In addition, doing the FRONT without doing the BACK is looking for trouble.. The system should be fully bled, AIR gets in the system from boiling and seepage and negatively affects clamping power causing imbalances.

See this thread, its a treasure trove of info and passionate behavior....

http://caddyinfo.ipbhost.com/index.php?sho...&hl=brakes&st=0

[epricedright]

Ok, I just read that brake post and all I can say is "I can't believe I read the whole thing" Wow that was long...along with all the other posts and articles I've read...I'm ready for a nap! I've read so much about brakes today I can't take anymore! All I can say for sure is I'm still not sure.

I wonder how the Quiet Stop Ceramic pads would do with a set of Powerstop or SP Performance cross-drilled/slotted rotors? Not sure if I'll need both drilled and slotted? I'm leaning more towards the Powerstops, but I don't have a price yet. I hate the idea of going back to them dirty, dusty semi-metalics, with my new chrome wheels. The ceramics definately spoiled me in that regard. The hot pads might work ok with the cooler rotors, I'm thinking. With the drilled rotors keeping the heat of the pads lower, I may not have the problem with excessive pad transfer onto the rotors, therefore preventing shudder. What do you guys think? Can drilled rotors be turned?

[robert383]

Mike,

Thanks for the links and will read the posts in this thread many times, prior to replacing pads, when the time comes. Very informative. Both my 97 STS and 94 DCS have/had brake issues that for the most part were/are annoying. My STS, braking from 55, fine. 70 and above, will shake you out of the car. Hope to make the right decession when it comes time for new pads and put some of the miths to rest.

[Ranger]

Mike,

Thanks for the links and will read the posts in this thread many times, prior to replacing pads, when the time comes. Very informative. Both my 97 STS and 94 DCS have/had brake issues that for the most part were/are annoying. My STS, braking from 55, fine. 70 and above, will shake you out of the car. Hope to make the right decession when it comes time for new pads and put some of the miths to rest.

I had the same problem, though not real bad. Had the rotors surfaced under warranty and braking is smooth now.

[epricedright]

Update. A couple weeks ago, right before my trip to Fl, I replaced my front brake slider bolts and sleeves ($24 for 4 OEM sets at partszoneonline.com....much more at my local dealer btw) and OEM rubber boots. My slider pins were not in too bad of shape, but I replaced them anyhow, as I had them on hand. I cleaned off the mating surfaces where my caliper slides on the knuckle with a wire brush attachment on my drill and a dremel tool and lightly greased that area. I also wire brushed the mating surfaces of my rotors and hubs, and honed the hole where my boots go in. I then had my front rotors turned, and my front brake shudder is now gone. I still have a very slight shudder, but I can tell that shudder is coming from the rear brakes. The front shudder, which was so bad and obnoxious, my hood would shake and vibrate violently, is now gone.

Last year, when I replaced my brakes, I mistakenly used petroleum grease in my new boots and not silicone. The grease was only on the boots for maybe an hour tops before I realized I used the wrong grease. I then cleaned the petroleum grease off and even soaked the boots in Dawn to remove any remants of the grease, and then used the correct silicone grease, but maybe the damage to the boots from the petroleum grease was already done. I learned from trial and error petroleum grease will cause the rubber boots to swell and expand.

My conclusion (theory) for my brake shudder is my brakes were not releasing all the way due to the pins were seizing in the boots, causing my rotors to warp. One of my pins was actually very hard to remove from the caliper (seized in the boot). Being my pads weren't "floating" like they should have and releasing from the rotor, they were causing my rotors to overheat and actually WARP. This explains why my shudder would dramatically increase when the brakes were hot (being metal expands when hot). That also explains why my shudder would worsen after driving for awhile, even when not using my brakes. The guy who turned my rotors said the one rotor was warped so bad, it had to be turned twice. I've read numerous articles where people claim rotors don't actually warp, and I'm sure in many cases, uneven pad deposition is the cause for shudder. But in my case, the theory that rotors don't warp was busted as there's no doubt in my mind my rotors were warped. Why else would the shudder worsen when the brakes were hot, and lessen when they were cooled?

I need to replace my rear pins and boots next as I think those boots were contaminated with petroleum grease as well. I will have those rotors turned, and all should be fine.

[BodybyFisher]

I believe you said your pads were worn unevenly. Meaning that the front of the pad or the first to contact the rotor was digging in. I would venture a guess that the guy that said it needed to turn it twice was seeing the impact of this digging in, AND..... he was seeing THICKNESS VARIATION, which when the rotor face sits on a flat surface appear to be warping...

[epricedright]

I believe you said your pads were worn unevenly. Meaning that the front of the pad or the first to contact the rotor was digging in. I would venture a guess that the guy that said it needed to turn it twice was seeing the impact of this digging in, AND..... he was seeing THICKNESS VARIATION, which when the rotor face sits on a flat surface appear to be warping...

I don't recall saying my pads were worn unevenly. You must be mistaking me with someone else. Now that you mention it though, one pad on one side was worn a little more than the other....maybe a 1/16"...hardly noticable at all. I attributed that to the slider pin sticking in the boot, causing it to wear faster being it was constantly rubbing my rotor. If I did have a "thickness variation", and not warpage, why would my brakes shudder more when the brakes were hot?

Mike, I know you're a firm believer that rotors don't warp. Do you have a theory that could explain why my brakes were shuddering drastically more when my brakes were hot and much less when they were cool? Being metal does expand when heated, and contracts when cooled, and being I had a sticky pin, my rotor warpage when hot theory makes sense to me.

[BodybyFisher]

I think this one will remain a mystery. I don't know why it would shudder more while hot. Next time mine shutter, I am going to MIC them and use a straight edge on them to see what is going on.

Sit and think about the idea of a rotor warping. While thinking about that consider the entire rotor, where the hub and wheel stud holes are and consider that that area is torqued to 100 ft. lbs. The flat area between where the wheel studs are and the braking surface is, is is a given, that distance is a constant. So where would the rotor warp, so that it could be machined enough to stop pulsing when machined.

Consider that the calipers apply opposing pressure on the braking surface by sqeezing this area with the caliper piston pushing the brake pads into the surface on one side, and pulling the pads into the surface on the other. Thickness variation from any reason would cause the pads to have to run over a surface that effectively had hills in it, when the hill increased the grab would increase.

My question is where would the rotor actually warp from so that it could actually be machined back into true form? I believe that for the rotor to warp like a CD in the sun?, the flat area where the hub and wheel stud holes are would also need to warp. I wish you measured yours with a MIC....

[epricedright]

I'm no metallurgists, but I would think the rotors warped in the area where it contacted the pads. I believe they were slightly permanently warped, or maybe even had uneven pad deposition, reason I would always have a slight shudder, and would warp when they got hot from the sticking slide (causing the violent shudder), and that warped rotor would return back to near normal once cooled. I believe either the slight warpage or uneven pad deposition was removed from the rotor when it was turned, and the warpage never reoccured due to the sticky pin was fixed.

I'm sure most cars that shudder are due to uneven brake deposition on the rotors, and the resulting shudder would not be affected by heat (shudder always present). But in my case, being the shudder was much more pronounced when hot, I feel the violent shudder was due to an overheated warped rotor.

I'm guessing my rear brakes shudder is due to uneven pad deposition on the rotors and a clean-up cut would fix it. I imagine I smoked them pretty good awhile back when I was trying to determine if the shudder was coming from the front or back brakes by braking the car with only my emergency brake. The rear shudder doesn't get worse when hot, so I doubt any warpage has occured. If I had the time and energy, I would just do a clean up cut and see if that fixes my shudder. But being it will be disassembled, I will replace my boots and pins and clean up all sliding and mating surfaces, just to be certain it's fixed.

If the front shudder ever reappears (heaven forbid), I will replace my front rotors with cross drilled, slotted rotors, (which are supposed to stay cooler) being the entegrity of my current rotors may have been compromised due to the overheating and turning.